In an uplink of a wireless communications system, because a radio channel is characterized by frequency selective fading, a base station 110 (BS 110) needs to schedule a user equipment (UE), so that the UE can perform data transmission on a frequency band with relatively good channel quality, obtain a frequency selective gain, and ensure uplink performance.
The BS 110 configures the UE to transmit a sounding reference signal (SRS) for estimating uplink channel quality. Then the BS 110 performs frequency selective scheduling for uplink data transmission of the UE according to detected channel state information (CSI).
In an existing Long Term Evolution (LTE) protocol, the UE sends an SRS based on two trigger mechanisms: a trigger type 0, or a trigger type 1. The trigger type 0 corresponds to periodic SRS transmission, and results in the triggering being performed using higher layer radio resource control (RRC) signaling. The trigger type 1 corresponds to aperiodic SRS transmission, and results in the triggering being performed using downlink control information (DCI) of a physical downlink control channel (PDCCH) or an enhanced physical downlink control channel (ePDCCH).
However, for the existing aperiodic SRS transmission, a DCI of a PDCCH or ePDCCH can be used to configure only one UE to send an SRS once. When an SRS needs to be rapidly configured for a plurality of UEs in a short time in the wireless communications system, the system has relatively large signaling overhead.